LEDs have numerous current and potential uses as light sources in various commercial applications including computer displays, residential and business interior lighting, outdoor lighting, signage, signals, and televisions. However, there are several problems with conventional LEDs. Conventional LEDs are typically packaged singly or with a small number of devices in each package. Such conventional packages usually employ low voltages with high driving currents. The higher the drive current, the more heat is generated in each LED. This requires mechanisms to dissipate the heat including heavy and expensive heat sinks or active cooling such as fans. Both mechanisms greatly increase the packaging cost and make it more difficult to use large numbers of LEDs, particularly in a small area.
More recently, LED arrays have been formed. These arrays typically use multiple horizontal-emitting LEDs that require the same high drive currents and result in the same heat dissipation problems as non-array packages. Although some vertical-emitting LED arrays have been formed, these arrays typically have complex designs that are expensive to fabricate and have low fabrication yields.
High-voltage LEDs are also known. These LEDs operate at a high voltage and thus draw substantially less current during operation. As a result, less heat is generated by these high-voltage LEDs. For example, for LEDs having output power dissipation of 1 watt, a low-voltage LED of 3V uses a 350 mA drive current; however, a high-voltage LED of 50V requires only a 20 mA drive current.
There remains a need in the art for improved LED arrays that generate low levels of heat while producing a high lumen output. There is a further need in the art for LED arrays that can achieve these features while also being extremely reliable in the event of a failure of one or more LEDs in the array.